This section is intended to introduce various aspects of the art, which may be associated with one or more embodiments of the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present disclosure. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Bend stiffeners are used in offshore flexible pipe and umbilical applications. Bend stiffeners are typically used with flexible pipes and umbilicals in the hang-off zone. Bend stiffeners typically have a truncated conical shape and are used to limit bending stresses to within acceptable levels at an end of the flexible pipe or umbilical where such is connected to an offshore structure located on a body of water or other rigid structure. The conical shape provides for a decreasing stiffness between the rigid structure and the unrestrained flexible pipe or umbilical. U.S. Patent Application Publication Number 2015/0136264 A1 describes the use of a bend stiffener at the end of a flexible pipe segment connected to a rigid end fitting.
Bend restrictors may also be used along a conduit to limit bending to a maximum value. Bend restrictors are typically articulated which allows flexing but limits the bend radius to a maximum. Bend restrictors thus do not limit stiffness and accordingly do not significantly improve the fatigue performance (fatigue resistance and/or fatigue life) of the underlying conduit. International Patent Application Publication Number WO 2015/071684 A2 describes the use of an articulated bend restrictor placed along a length of a flexible pipe to limit the bend radius. The described bend restrictor has fixed end sections with a plurality of intermediate sections disposed there between. The intermediate sections alternate male sections and female sections held in position by the fixed end sections.
Unlike flexible pipes, umbilicals, cables, and the like, rigid steel risers are manufactured by girth welding steel pipe joints to form the rigid riser. Using rigid risers in offshore applications can give rise to areas where the rigid riser experiences high fatigue, such as within the touchdown zone and/or the hang-off zone. The girth weld joints of a rigid riser are susceptible to fatigue. When dealing with a rigid riser system, high performance girth welds are currently utilized to improve the fatigue performance within the high fatigue areas of the rigid riser. High performance girth welds utilize costly welding consumables and require controlled welding conditions in order to control the heat affected zone within the girth weld joint. High performance girth welds also require fatigue testing to confirm the fatigue performance whereas lower performance girth welds merely require workmanship inspection or no inspection at all. High performance girth welds, therefore, increase the cost and efficiency of manufacturing rigid risers.
Thus, there is a desire to provide a fatigue performance enhancer that provides enhanced fatigue performance (fatigue resistance and/or fatigue life) of girth weld joints within a rigid riser. In one aspect, the fatigue performance enhancer improves the fatigue performance of a lower performance girth weld joint allowing the use of lower cost and more efficient girth welding processes in the manufacture of a rigid riser to obtain similar fatigue life as high performance weld joints or improves the fatigue performance of a higher performance girth weld joint allowing the use of rigid risers in more challenging offshore environments where use was previously prevented due to the fatigue limitations of the girth weld joints.